Abstract

Friction stir lap welding (FSLW) of thin aluminum sheets in industry and in research has faced challenges in weld quality that limit welding speeds. Interfacial defects such as hooking and thinning are common defects that appear at the interface of FSLW, and researchers and process operators have traditionally reduced process parameters such as feed rate and spindle rotation to fully eliminate the defects. While such measures are successful in creating fully consolidated FSLW, feed rates for FSLW have stagnated around 1 mpm with the fastest feed rates recorded at 3 mpm, making it difficult for manufacturers to implement FSLW in production. In this study, a novel tool geometry is implemented and demonstrated to fully eliminate the thinning and hooking defects and perform friction stir lap welds at feed rates 3x faster than the fastest recorded FSLW process speeds. This thesis will characterize friction stir lap welds made at 10 mpm. A range of weld parameters resulting in repeatable fully consolidated welds will also be provided. All weld parameters were assessed for weld quality through CT Scanning and optical microscopy of weld interfaces, observing interfacial mixing and measuring area of consolidation. Welds made at nominal weld parameters were further assessed through microhardness testing, tensile and fatigue testing, pressure testing, and electron backscattering diffraction. It was demonstrated that loading direction of the weld had a significant impact on performance, with the advancing side proving to be stronger than the retreating side under load.

Degree

College and Department

Ira A. Fulton College of Engineering; Manufacturing Engineering

Rights

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